NAD amplifier repairs

[nukaidee]

I hope this is the right forums. I'm not even sure if its a "solid state". Anyhow, I have 2 NAD amps which .. don't work. Basically I can get power but the relays are not engaging. can someone point me out a place to start?

thanks

[Jan Dupont]

Right forum
You can start by telling what's the model name of the NAD amps ?

[nukaidee]

the one i want to get moving is the nad3150. the other one is in storage somewhere, its rotting away and if i don't get that one going I will hurt less. I've cleaned all the pots , connectors etc. Checked for shorts in the binding posts and inputs. When I power it on, the protection led lights, so therefore I'm guessing thats stopping the relay.

I've tried searching for schematic, but seems like no one knows this amp..

edit: nevermind! I found the schematics for it! linked here..

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[Jan Dupont]

Try disconnect the pre and power amp on the back side of the amp by removing the phono jumpers at start it up again. If the protection is still on, then the fault has been located to the power amp section......

[nukaidee]

the phono jumpers, you mean the two metal rods that are in the rca inputs? .. no difference..

[Jan Dupont]

Yes those... It's properly a faulty driver or output transistor. Now you need to do some measurements. How are your skills and what tools do you have ?

[nukaidee]

I've been building electronics for the last 10 years or so. Done everything from microcontrollers to ham radios. I feel comfortable with high voltages and I'm pretty handy with a soldering iron / voltmeters etc. I've got your basic handyman's tool kit. I do not have access to an oscillator/scope tho.

[Jan Dupont]

Ok
You can find the schematic (sadly poor quality) on my website;
Schematics and Service Manuals
With power on, check if one channel is putting out a high level of DC (measure this before the protection relay)

[nukaidee]

I linked the schematic on my second post too. Im looking at yours too now. I think I need to decode the schematic to where it is on the pcb. ugh...

[Jan Dupont]

I think I need to decode the schematic to where it is on the pcb. ugh...

Yes. Now to the fun part